Device for Spreading a Foil Web

ABSTRACT

A device for spreading foil webs, with the device guiding apart the strips of a foil web that has been separated into at least two web sections in such a way that at least two packages can be packed, i.e. in particular wrapped, simultaneously in parallel next to each other. The foil web that has been separated into at least two web sections is guided over at least two adjustable bodies, said bodies including microopenings at least in the area whereover the foil is guided, with said microopenings being impingeable with compressed air. Preferably, the bodies can be arranged at an angle relative to one another. A method is also provided for separating and guiding the foil web, which has been split into at least two web sections, by a device wherein the described foil web is guided over bodies that are at least adjustable and impingeable with compressed air. According to the invention, the foil web is held at a distance from the said bodies with the aid of a multitude of fine-pored openings that are impingeable with compressed air.

This claims the benefit of German Patent Application DE 10 2009 026 059.5, filed Jun. 29, 2009 incorporated by reference herein.

The present invention relates to a device for spreading a split foil web as well as an appropriate method.

BACKGROUND

In the packaging industry, packages are often conveyed through appropriate packaging machines for the (outer) packaging of said packages by means of multi-lane conveyors. In particular, at least two packages at a time are parallely wrapped up, at least partially, in packaging foil during a single enveloping process. For this purpose it is necessary to split the packaging foil web, which is usually available as a single web, into at least two web sections by means of a cutting device and a spreading device located downstream from said cutting device. The provided wide foil web is split into at least two halves in this way, and the said two halves are positioned at an adequate distance from each other so that it is possible to envelope two packages conveyed in parallel next to each other without the said two halves of the foil web interfering with each other.

Currently, the spreading of the foil is generally performed by pulling the foil, which is split into two web sections, over angularly inclined, non-rotating spreader rolls. In order to minimize friction at the non-rotating rolls, the said rolls are equipped with drilled holes along a section of their perimeter, so that air flows out of said holes. The said section of the rolls corresponds to at least the wrap angle of the foil. The roll that is impinged with compressed air hereby creates an air bearing for the foil web.

Alternative variants may allow for omitting the air bearing, and merely guide and pull the foil over a curved shaft. This variant, however, has the disadvantage that the foil becomes electrostatically charged and can only be slightly spread apart, typically resulting an a foil spacing of no more than approximately 30 mm.

A device for separating a material web into two web sections by longitudinal cutting and subsequent usage of a foil spreader with deflection bars for guiding the foil is for instance known from DE 42 41 354 C1. In this instance, the spreading is performed by deflection bars that can be adjusted with regard to their spreading degree, whereby said bars are formed as hollow profiles that are impingeable with compressed air and comprise a plurality of openings for emitting the compressed air.

EP 710 531 B1 shows a device and a method for longitudinally slitting strip material by means of rotating knives. The invention in particular relates to an improved method for slitting web sections involving razor blades, with minimal spreading of the web sections and attendant defects, whereby the web section is guided on an air support consisting in particular of a cylindrical air support bar that is equipped with holes. In the ensuing process of unwinding and transporting, the foil that is cut to a defined length is conveyed on a so-called vacuum belt towards the foil wrapping station. Due to the given mechanics of two separate belts along the transport route from the foil separating station to the vacuum belt and to the conveyor belt and the foil wrapping, the foil has to be conveyed or, as the case may be, pushed along an area where support of the foil cannot be ensured. In order to bridge this area and in order to ensure that the foil or the starting end of the foil is not folded away due to gravity, thus causing production disruption, the foil is stabilized with the aid of two blowing tubes and conveyed in the desired position and alignment by means of an air channel created by one of the blowing tubes.

DE 37 33 129 A1 discloses a device for separating the material web into at least two partial web sections. In this connection, the web sections are guided past adjustable deflection members, the position whereof is controllable by controlling members of the material web as well as of the individual web sections.

DE 42 07 725 C2 describes a device providing a longitudinal cutting apparatus between the foil roll and the dancer, with said apparatus cutting the supplied foil web in the middle, whereafter the thus resulting two foil web sections are advanced along a foil spreading device to the respective packaging stations

DE 101 05 486 A1 describes a method and a device for producing packages with an outer wrapping. In this connection, a foil web of double width is centrally separated for creating individual foil web sections. The material strips are spread by means of deflection rollers arranged at an axial distance relative to one another.

DE 100 23 169 A1 discloses a double acting spreading device which guides the material web apart by means of two arrow-shaped turning bars that are arranged to be fixedly connected to one another at the same obtuse angle. In this connection, the uncut web is conveyed to and from the arrow-shaped turning bars at the levels of said bars.

DE 10 2004 018 981 A1 discloses a spreader roll for the crease-free guiding of foils and material webs by means of spreading elements, whereby the said spreading elements, which are guided in a roll, are slightly pressed together by the pressure of the material web and thereby move outward. A spreading element consists of a contact rail, resilient intermediate strips, and a guide rail, with the possibility of impinging the contact rail with pressure.

EP 1 634 831 A1 shows a web spreading method and a web spreading device. The spreading device operates by means of adjustably arranged cylindrical elements. The webs are conveyed over deflection means comprising, on their cover surfaces, holes for blowing air, said holes being intended for reducing friction.

U.S. Pat. No. 4,176,775 describes a spreading device for strips of slit web, whereby the web strips are guided over spaced, bowed spreader bars and thereby separated from one another. A layer of air here also serves for reducing the friction.

The systems described are generally disadvantageous in that they require a system for compressed air. In addition, the stabilization and conveyance of the foil sections by compressed air result in a relatively high consumption of compressed air, necessitating a relatively high energy input for producing the said compressed air.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a possibility for spreading and guiding split strip and foil material in a packaging machine with said possibility being easy to handle, operating reliably, and being energy-saving.

A packaging machine for wrapping packages comprises, among others, a packaging station with an enveloping device. In such a packaging station the packages are commonly supplied in at least two rows. The packaging material employed is accordingly required in at least two webs. The present invention in particular relates to devices for spreading foil webs in connection with packaging machines wherein packages are enveloped in cut-to-length foil webs and subsequently undergo a shrinking process, as the case may be.

The packaging material employed, i.e. in particular the foil, is commonly available in a single web on a roll. In order to employ the foil for wrapping the packages, it is necessary for one thing to longitudinally separate the foil web and for another thing the web sections to be spread.

The present invention provides a device for spreading with the said device guiding apart the strips of a foil web that has been separated into at least two web sections in such a way that at least two packages can be packed, i.e. in particular wrapped, simultaneously in parallel next to each other. The foil web that has been separated into at least two web sections is thereby guided over at least two adjustable bodies, said bodies comprising openings at least in the area whereover the foil is guided, with said openings being impingeable with compressed air. Preferably, the said bodies can be arranged at an angle relative to one another. According to a preferred embodiment, the angle can be adjusted in such a way as to make it possible to variably adjust the degree of spreading.

According to the invention, said bodies are made from a fine porous material, at least partially in the area whereover the foil is guided. Preferably, a ceramic material is employed. According to a preferred embodiment, the fine porous material employed is aluminum hydroxide (Al(OH)₃).

The fine porous material comprises microstructures, such as for instance a pore diameter between 5-10 μm. The invention is not to be limited to the material described here, but rather comprises all comparable materials with air-permeable microstructures.

According to a preferred embodiment, the guide bodies are cylindrical, hollow bodies, whereof the surface is partially or completely made from the fine porous material. According to a further embodiment, the bodies comprise a curved surface in the area over which the foil is guided, said bodies being made from the fine porous material described, while on the side or surface opposite having no contact with the foil web other materials and surface structures, respectively, may be employed. These sides or surfaces also do not require to be impingeable with compressed air, i.e. in particular they do not need to be air-permeable.

Furthermore, the invention relates to a method for separating and guiding the foil web, which has been split into at least two web sections, by means of a device in which the described foil web is guided over at least two bodies that are adjustable relative to one another and impingeable with compressed air. According to the invention, the foil web is held at a distance from the said bodies with the aid of a multitude of fine-pored openings that are impingeable with compressed air. This is possible due to the above-described microstructure of the bodies in the area whereover the foil is guided. The microstructure may be limited to said area over which the foil is guided, or it may alternatively encompass the entire bodies.

The invention is based on the employment of a specific manifestation of an aerostatic bearing system. The underlying basis is a planar, fine porous, aerostatic bearing unit that may be formed, for instance, as a cylindrical element. The impingement with compressed air results in an outflow of air. Due to the fine porous structure, this outflow of air is planar and homogenous in the area of said fine porous structure. In comparison to the other known systems that produce an aerostatic bearing, for instance by impinging cylindrically shaped elements comprising drilled holes with compressed air, the air consumption in this system can be reduced. This leads to reduced energy consumption at the same time.

In particular, the invention may be employed with a packaging machine for handling the packaging foils in the functional areas for spreading the foil.

In the described application, the air supported, angularly arrangeable and stationary spreader guides are substituted by an appropriately assembled air bearing. The planar air film streaming out of the fine pores causes the foil to be pulled over the spreader rollers nearly without contacting said rollers and to be spread by their angular position relative to one another.

The essential advantage of this system as opposed to the systems as described in prior art consists in the massive reduction in air and energy consumption.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following passages, the attached figures further illustrate exemplary embodiments of the invention and their advantages. The size ratios of the individual elements in the figures do not necessarily reflect the real size ratios. It is to be understood that in some instances various aspects of the invention may be shown exaggerated or enlarged to facilitate an understanding of the invention.

FIG. 1 shows a schematic illustration with functional elements of a packaging machine;

FIG. 2 shows a schematic side view of a foil web being deflected and spread in a packaging machine according to FIG. 1, and

FIG. 3 shows a schematic illustration of the adjustable bodies being impingeable with compressed air.

DETAILED DESCRIPTION

The same or equivalent elements of the invention are designated by identical reference characters. Furthermore and for the sake of clarity, only the reference characters relevant for describing the respective figure are provided. It should be understood that the detailed description and specific examples of the device and method according to the invention, while indicating preferred embodiments, are intended for purposes of illustration only and are not intended to limit the scope of the invention.

FIG. 1 illustrates a packaging machine 10. The said packaging machine 10 comprises a guide system 20 for supplying foil webs 22 to pre-assembled packages 30. In particular, the foil webs 22 involved are cut-to-length foil webs and/or split foil webs 22 being longitudinally guided in parallel by twos or more and spaced apart from each other. The foil is supplied by the meter on a foil drum 24. The guide system 20 may in particular be formed as a dancer for the intermediate storage of the required length of foil.

The packages 30 to be enveloped by the foil webs 22 comprise at least two rows of assembled bodies, whereby said packages are conveyed on an horizontally arranged conveyor 40, in particular a conveyor belt, to the packaging station 12. At the packaging station 12, the packages 30 are enveloped and wrapped with appropriately cut-to-length foil webs 22 by means of an enveloping device 14. Subsequently, the wrapped packages 30 can be conveyed, for instance, to a shrink tunnel, in order for said packages to undergo a shrinking process under the influence of heat.

In the depicted exemplary embodiment, the foil webs 22 are withdrawn from a foil drum 24 prior to spreading, and then cut longitudinally into sections of appropriate width by means of a cutting device 42, thus ensuring endless conveyance over a longer period of time. It is possible to activate another foil drum 26 before the foil from the foil drum 24 is completely used up, with said new foil drum 26 being preferably ready on stock in the packaging machine 10. Furthermore, it is possible to monitor the state of foil drum 24 by means of a detection system and to transmit a signal to a control device in time for the said control device to initiate the supply of a new foil drum 26.

The designated detailed view 60 is explained more fully below by reference to FIG. 2.

The schematic side view of FIG. 2 shows a detailed illustration of the foil web being deflected and spread by means of a deflection and spreading device 60 of the packaging machine 10 from FIG. 1. The foil web is deflected over the deflection and spreading device 60 a number of times—twice in the depicted exemplary embodiment. In the exemplary embodiment shown here, the depicted deflection and spreading device 60 comprises two pairs of rolls 621 and 622, respectively, which are illustrated in more detail in FIG. 3.

FIG. 3 illustrates a pair of rolls 621 and 622, respectively. It is thereby possible to arrange the two rolls 62 at an angle relative to one another. The rolls 62 are, for instance, cylindrical, hollow bodies made from a fine porous material with micro openings. The fine porous material may be made of, for instance, ceramic material with a pore cross-section between 5 and 10 μm. The outflow of air from a cylindrical, hollow body made of the material specified above or of a comparable material differs from the outflow from hollow bodies having been equipped with holes by means of a drill. Due to the microstructure of the material employed, less air is required than when employing conventional air openings for creating an equally effective air film or for creating the same air bearing effect.

Furthermore, it is possible to produce the hollow body from a granular material of aluminum hydroxide Al(OH)₃, which also features a microporous structure, with said structure being air-permeable. The employment of other materials with comparable characteristics shall also be comprised by the invention.

In the depicted exemplary embodiment, the spreading of the longitudinally cut web sections is performed by means of two pairs of rolls 621 and 622. The foil web 22 is supplied from the foil roll 24 and cut longitudinally. The therefrom resulting narrower foil web sections 22 are guided over a first pair of rolls 621. As the rolls 62 are arranged at an angle relative to one another in the pair of rolls 621, this results in spreading apart the two web sections 22. Subsequently the foil webs 22 are guided vertically upwards to a second pair of rolls 622, wherein the rolls 62 are, again preferably, arranged at an angle relative to one another so that a further spreading is possible—if this is desired for the further processing.

In this manner, the distance required between the partial web sections 22 for the downstream packaging machine can be simply created. This distance can be appropriately varied according to the angle at which the rolls 62 are arranged in the first pair of rolls 621 and/or in the second pair of rolls 622.

In order to prevent strong forces to act on the foil webs 22, with said forces possibly leading to warping the web sections and thus interfering with the downstream packaging process, it is advantageous to minimize friction between the rolls 62 and the web sections 22. For this reason, an air bearing is advantageous, in particular an air- and energy-saving air bearing, which may be created with the aid of the microstructure as described above.

The invention has been described with reference to preferred embodiments. Those skilled in the art will appreciate that numerous changes and modifications can be made to the preferred embodiments of the invention and that such changes and modifications can be made without departing from the spirit of the invention. It is, therefore, intended that the appended claims cover all such equivalent variations as fall within the true spirit and scope of the invention.

LIST OF REFERENCE CHARACTERS

10 Packaging machine

12 Packaging station

14 Enveloping device

20 Guide system

22 Foil web

24 Foil drum

26 Foil drum

30 Package

40 Conveyor

42 Cutting device

60 Deflection and spreading device

62 Roll

621 Pair of rolls

622 Pair of rolls 

1. A device for spreading a foil web split into at least two web sections for a packaging machine for wrapping packages with the foil web, comprising: at least two adjustable bodies for guiding the split foil, the adjustable bodies at least in an area over which the foil is guided including a fine porous material defining openings capable of delivering compressed air.
 2. The device as recited in claim 1 wherein the bodies are cylindrical, hollow bodies.
 3. The device as recited in claim 1 wherein the fine porous material is a ceramic material.
 4. The device as recited in claim 1 wherein the fine porous material is aluminum hydroxide (Al(OH)₃).
 5. The device as recited in claim 1 wherein the fine porous material has a pore diameter between 5-10 μm.
 6. A method for separating and guiding a foil web split into at least two web sections by a device, comprising: guiding the foil web over at least two adjustable bodies capable of delivering compressed air; and holding the foil web at a distance from the bodies with the aid of a multitude of fine-pored openings delivering the compressed air. 